What’s the evidence?

Introduction

It is now very widely accepted amongst scientists that nutrition is of fundamental importance in protecting against the development of cancer. This fact has been highlighted by many key organisations and scientific groups not least the World Cancer Research Fund who have said that a third of the most common cancers could be prevented through a nutritious diet, maintaining a healthy weight and regular physical activity.

Regarding the role of nutrition in the support of people diagnosed with cancer, currently this remains a controversial issue. Although there is growing evidence that a healthy diet as well as nutritional and herbal supplements can positively influence the health of those with cancer, there is little consensus and few guidelines as to the most appropriate approach.

The dietetic versus nutritional therapy approach to cancer support

Currently there is relatively little attention given to the nutritional needs of cancer patients within the mainstream healthcare setting. However, some support does exist and within hospitals dieticians provide information on how best to deal with the side effects of treatment or symptoms of the disease. Dietitians are skilled in managing acute problems relating to nutrition such as swallowing problems and lack of absorption due to the disease or treatment, both of which may require artificial tube feeding in extreme cases. However, dietitians don’t usually advise on how to use nutrition to strengthen the body and increase resistance to cancer.

The aims of a nutritional therapist supporting someone with cancer will be to minimise symptoms of the disease and side effects of treatment; and importantly also to increase overall health and resistance to the disease. Many nutritional therapists in the UK are trained in Functional Medicine, an approach which focuses on identifying and addressing the underlying causes of disease and, taking account of the evolving research in nutritional science including nutrigenomics and biochemical testing, will design a nutrition and lifestyle programme that is tailored to the unique needs of the individual (Pizzorno).

The Body Soul Nutrition approach to cancer support

At Body Soul Nutrition we use an approach that combines functional medicine with naturopathy (for more details see the Our Approach page on our website). The work we do is ‘evidence informed’ meaning that it is in line with the latest scientific evidence on nutrition and cancer, but not based solely on this evidence. The reason we look beyond the scientific literature to also consider traditional practices, the latest expert opinion, and also the abundance of anecdotal evidence is that funding for large-scale nutritional clinical trials is scarce and there are therefore gaps in the current evidence. Of course, we also draw on our collective experience as a team and importantly we also use our intuition so that our work encaptures the true essence of healing support and becomes an art as well as a science.

The work we do is ‘evidence informed’ meaning that it is in line with the latest scientific evidence on nutrition and cancer, but not based solely on this evidence.

Research evidence

When considering the evidence underlying the use of nutritional support in cancer, it’s important to take a broad perspective. As, whilst there are still relatively few human intervention trials looking at dietary therapy and cancer, there are many other types of evidence that lend weight to the argument for using nutritional approaches to support those with cancer.

Cancer prevention studies

A large amount of epidemiological evidence, where the patterns, causes and effects of health and disease are studied in whole populations, suggest that dietary factors can either increase or decrease the risk of cancer. Factors that appear to increase risk include a high intake of processed meats, high calorie diets that lead to obesity, and alcohol. Factors that appear to protect against cancer include a high intake of plant foods such as vegetables and fruit. In 2007 the World Cancer Research Fund conducted the largest ever review assessing the cancer prevention research data (WCRF 2007), full details of this and their ongoing work can be found on their website.

Epidemiological evidence has its limitations and can only highlight areas where there are possible associations rather than definite causes and effects. However, the cancer prevention data is important as it is so abundant. This data, that gives us clues to the possible dietary factors that influence cancer risk, is relevant not just in helping prevent cancer but also when considering the nutritional needs of people already diagnosed, as evidence suggests that at least some of the mechanisms of primary cancer development are the same as those involved in secondary cancer development (Knowles). This means the diet that helps to prevent a primary cancer may also reduce the risk of a secondary cancer and will also likely reduce the chance of primary cancer recurrence.

Laboratory and animal studies

Cancer dietary epidemiological findings are supported by the many basic science studies that have provided mechanisms for the effects observed. In particular, there are an abundance of studies demonstrating the anticancer effects of nutrients and associated compounds extracted from our plant foods.

Studies show that compounds present within the plants we eat, as well as plants used as herbal remedies, influence just about every cancer pathway that has ever been discovered. From the initiation, to the promotion, to the progression stages of cancer plant compounds have been shown to have direct anticancer effects (Orlikova). These compounds influence gene expression, they alter the metabolic and biochemical behaviour of cancer cells, they modulate the tumorigenic microenvironment, and they also target cancer stem cells (Pratheeshkumar, Torquato), something that has been difficult to achieve with mainstream chemotherapy drugs. They also have a powerful non-direct influence on the cancer process by modulating the immune response. There are many, many compounds with anticancer activity, but some of the most well-studied include curcumin from turmeric, sulforaphane from cruciferous vegetables, genistein from soya and epigallocatechin from green tea (Wang). As this area of science rapidly develops, a number of databases have been set up in an attempt to collate the vast amount of data relating to these natural compounds and their anticancer effects (Choi).

Human intervention studies

Despite the growing interest in the enormous potential natural compounds hold in preventing and treating cancer it is still early days in terms of translating the basic science into human clinical trials. Human trials are expensive and funding is difficult to come across unless there is to be some ultimate gain for the pharmaceutical industry, which means that the investigation of the clinical effects of natural compounds and diets are a neglected area of medical science. Having said this, studies do exist and given the many limitations of current cancer drug therapies, interest in this area is growing.

“A link between adopting a healthy lifestyle and a reduction in the rate of established cancer progression is now emerging in the published literature.” Robert Thomas, Oncologist and Researcher

As well as the potential for natural compounds to influence the development and progression of cancer, there is also the important consideration of how nutrition can help to ease symptoms of the disease and side effects of treatment, as well as support overall health and quality of life. There is no doubt that those with cancer often have greater and more complicated nutritional needs than the general population and evidence shows that survivors with a better nutritional status have fewer disease symptoms, a lower risk of treatment complications, longer survival times and an improved quality of life (Baldwin, Ko, Pan). Apart from improving general nutritional status, other evidence shows that specific nutritional interventions are effective in treating the symptoms and side effects of cancer and its treatment (Delia and Nicholson).

Overview of a selection of human trials

Of course, the cancer nutrition intervention trials are way too numerous to mention in full in this article but a selection of 10 studies have been highlighted below. Outcome measures vary in these and other studies, ranging from changes in cancer markers or other measures of disease progression, to changes in symptoms and quality of life, to changes in length of survival.

Diet studies

Chlebowski (2005) – prospective trial involving 2,437 post-menopausal women with early breast cancer. The women were chosen randomly to receive nutritional and lifestyle counselling, or not. The dietary intervention included eight bi-weekly individual counselling sessions. Dietary fat intake reduction was significantly greater in the dietary group. After 60-months follow-up, breast cancer relapse rates were significantly lower in the intervention group (p=0.03). This difference was even greater in the ER negative subgroup (p=0.018). There was a statistically significant improvement in overall survival in the intervention arm, although statistically significant for specific breast cancer recurrence only in women who were ER negative. Considering that weight loss was greater in the dietary group it may have been this rather than the lower fat intake that was responsible for the observed effects

de Groot (2015) – 13 women with Her2 negative breast cancer were randomised to a short-term fast (STF) 24 hrs before and after commencing chemotherapy, or to eat according to the guidelines for healthy nutrition. Toxicity in the two groups was compared. Chemotherapy-induced DNA damage in peripheral blood mononuclear cells (PBMCs) was quantified by the level of γ-H2AX analyzed by flow cytometry. Mean erythrocyte- and thrombocyte counts 7 days post-chemotherapy were significantly higher in the STF group compared to the non-STF group and levels of γ-H2AX were significantly increased 30 min post-chemotherapy in CD45 + CD3- cells in non-STF, but not in STF patients.

Gold (2009) – prospective dietary study involving 2,967 breast cancer survivors. The women were randomly assigned to receive a five-a-day dietary guideline or to enter a control group. The intervention significantly improved vegetable/fruit servings, fibre and fat intake compared to controls. Adjusting for tumour characteristics and hormonal treatment, women who did not experience hot flushes (no change was seen in those that did) had 31% fewer cancer-related events than similar women assigned to the comparison group

Ornish (2005) – randomised study involving 93 volunteers with early prostate cancer not undergoing conventional therapies. Randomly assigned to intensive nutritional counselling and lifestyle changes, or not, as part of their active surveillance. Lifestyle changes included a vegan diet supplemented with soy, vitamin E, fish oils, selenium, and vitamin C, together with a moderate exercise program and stress management techniques such as yoga. PSA levels decreased by 4% at 12-months in the intervention group, but increased by 6% in the control group; this was statistically significant. As a secondary end-point, serum taken from patients from the intervention group and introduced to prostate cell lines in vitro were eight times more likely to inhibit their growth than the control arm (70% v 6%). Furthermore, changes in PSA and cell line growth strongly correlated with the degree of lifestyle change

Ravasco (2012) – in an earlier randomized trial involving 111 patients with colorectal cancer, group 1 received individualized nutritional counselling and education about regular foods, group 2 received dietary supplements and consumed their usual diet of regular foods, and group 3 consumed their usual diet of regular foods. Nutritional counselling during radiotherapy was found to be highly effective at reducing acute radiotherapy toxicity and improving nutritional intake/status and quality of life. Efficacy persisted for 3 months after the intervention. In this later study analyses and comparisons between groups were performed after a median follow-up of 6.5 yrs. Nutritional deterioration was higher in group 3 and group 2 than in group 1 and adequate nutritional status was maintained in 91% of group 1 patients but not in any of the group 3 patients. Median survival in group 3 was 4.9 y (30% died), in group 2 was 6.5 y (22% died), and in group 1 was 7.3 y (only 8% died). Late radiotherapy toxicity was higher in group 3 and group 2 than in group 1 and quality of life was worse in groups 3 and 2 than in group 1

Thomas (2006) – double blind trial involving 110 men with progressive prostate cancer. All men received monthly counselling on healthy lifestyle and were randomised to salicylate alone or salicylate plus dietary supplements (Vitamin C, copper and manganese gluconate). The analysis at twelve-months showed no additional benefit from the supplements but nearly 40% of the entire group demonstrated a significant slowing or halting of PSA progression

Supplement studies

Ohno (2013) – preliminary longitudinal clinical study to assess whether daily intake of the mushroom Agaricus blazei Murill (as granulated powder) for 6 months improved the quality of life (QOL) of 67 cancer patients in remission. The results showed a significant improvement in QOL with regards to both physical and mental components

Rao (2014) – single-blinded, randomized, controlled clinical trial involving 80 head and neck cancer patients receiving radiation therapy or chemoradiotherapy. Patients received either a turmeric gargle or the control: povidone-iodine during the period of treatment and oral mucositis was assessed using the RTOG (Radiation Therapy Oncology Group) grading system. The group using the turmeric gargle had delayed and reduced levels of radiation-induced oral mucositis, statistically significant at all time points. Additionally, the cohorts using turmeric had decreased intolerable mucositis and lower incidence of treatment breaks in the first half of the treatment schedule before 4 weeks. They also had reduced change in body weight

Sommacal (2015) – prospective, double-blind study of 46 patients undergoing surgery for periampullary neoplasms. The effect of synbiotics (probiotics + prebiotics) on nutritional status, postoperative complications, antibiotic use, length of hospital stay, and mortality were measured. The incidence of postoperative infection was significantly lower in the treatment group compared to the control group. Duration of antibiotic therapy was also shorter, non-infectious complications were less common, and mean length of hospital stay was shorter in the treatment group compared to control. No deaths occurred amongst those receiving synbiotics, whereas 6 deaths occurred in the control group

Thomas (2014) – 199 men with localised prostate cancer, 60% managed with primary active surveillance or 40% with watchful waiting following previous interventions, were randomised (2:1) to receive an oral capsule containing a blend of pomegranate, green tea, broccoli and turmeric, or an identical placebo for 6 months. The median rise in PSA in the food supplement group was 14.7%, as opposed to 78.5% in the placebo group

Summary

Whilst it is clear there is a need for a many more human clinical trials to further test the effectiveness of natural compounds and healthy diets in those with cancer, it seems important not to wait until the number of studies have increased before introducing these supportive methods considering their potential benefits and the fact that they have shown to be very safe if used appropriately.

Apart from the value for physical health, there is one other very important reason why nutritional interventions should be introduced at the earliest opportunity and this is the potential benefits for mental and emotional wellbeing. Research has shown that many people with cancer experience a psychological boost when they receive information and guidance on how to help themselves through positive lifestyle changes (Loh) and this psychological boost, which can counteract some of the stresses of a cancer diagnosis and its treatments, will translate into further gains for the physical body.